Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 2:13 PM GMT on September 21, 2010
Hurricane Igor is tenaciously hanging on as a Category 1 hurricane, and is causing trouble in Newfoundland, Canada. Winds at Sagona Island, over 100 miles to the northwest of Igor's center, were sustained at 68 mph, gusting to 86, this morning, and were 56 mph, gusting to 84, at St. Pierre. Offshore, at the Newfoundland Grand Banks Buoy, winds peaked at 56 mph and significant wave heights hit 39 feet as the center of Igor passed by. Rainfall amounts of 3 - 5 inches are possible for the capital of St. Johns, where winds are already at 29 mph, gusting to 43 mph. Weather radar out of St. Johns is estimating rainfall amounts of up to 1/2 inch per hour from Igor.
Figure 1. Hurricane Igor as seen by the MODIS instrument on NASA's Terra satellite at 11:15 am EDT Monday September 20, 2010. Image credit: NASA.
Potentially dangerous Caribbean disturbance 95L forms
A tropical wave (Invest 95L) moving westward at 10 - 15 mph though the Lesser Antilles Islands is bringing gusty winds and heavy rain to the islands this morning, and has the potential to develop into a dangerous Caribbean tropical storm or hurricane late this week. The wave brought sustained winds of 30 mph to Barbados this morning, and heavy rain squalls will continue over the Lesser Antilles today. Radar from Curacao and satellite loops show that 95L's thunderstorm activity is disorganized, though increasing in areal coverage and intensity. Wind shear over the Caribbean is very low, less than 5 knots, and is forecast to remain low for the rest of the week. Water temperatures and oceanic heat content in the Caribbean are at their highest levels in recorded history, so there is plenty of fuel for development. NHC is giving the disturbance a 20% chance of developing into a tropical depression by Thursday. I'd put the odds higher, at 30%.
The wave should continue moving westward near 10 - 15 mph through Friday, when it will arrive near the northern coast of Nicaragua. Most of the models show some development of 95L by Thursday or Friday, and the disturbance will bring heavy rains to the Netherlands Antilles Islands and north coast of South America on Wednesday and Thursday as passes to the north. Heavy rains may also spread to Southwest Haiti and Jamaica on Thursday. When 95L reaches the Western Caribbean Friday, steering currents will weaken and the storm will slow, potentially bringing life-threatening heavy rains on Friday and Saturday to northern Nicaragua and northern Honduras. If the center of 95L remains over water, the storm could easily develop into a powerful and dangerous hurricane over the Western Caribbean this weekend. With a strong trough of low pressure expected to dive southwards over the Eastern U.S. and form a "cut-off" upper level low over the Southeast U.S. this weekend, this potential hurricane could get drawn northwards across western Cuba into the Gulf of Mexico. Equally likely scenarios are that 95L will stay in the Western Caribbean, or that the storm will make landfall over Nicaragua and dissipate on Friday, and never reach the Western Caribbean. It is too early to assign probabilities on which of these three scenarios is the most likely.
Figure 2. Morning satellite image of the potentially dangerous Caribbean disturbance 95L.
Tropical Storm Lisa forms
Tropical Storm Lisa, the 12th named storm of this exceptionally active 2010 Atlantic hurricane season, is now churning over the waters of the far Eastern Atlantic. Lisa is currently in an environment of low wind shear, 5 - 10 knots, which is expected to continue through Thursday. Sea Surface Temperatures are a little cool, just 27°C, and there is some dry air to the north which may slow down development. Lisa is not likely to intensify into a hurricane, which would break our string of three straight major hurricanes that have developed (Igor, Julia, and Karl.) By Thursday, upper level winds out of the west are expected to increase, bringing high wind shear of 20 - 45 knots over Lisa for the remainder of the week. It appears unlikely that Lisa will affect any land areas.
Typhoon Fanapi deluges China
Typhoon Fanapi made landfall in mainland China about 150 miles east-northeast of Hong Kong Monday morning as a Category 1 storm with 75 mph winds, dumping the heaviest rains seen in a century to the southern Guangdong Province of China, according to the provincial weather bureau. Rainfall amounts of 550 mm (21.6") were recorded in the hardest-hit Shuangyao Township in Yangchun City. Thousands of people are stranded due to washed out roads and bridges in the region. In Taiwan, where Fanapi struck as a Category 2 typhoon with 105 mph winds on Sunday, the damage total is estimated at $210 million. Fanapi killed three people on the island, and brought rains of up to 1400 mm (4.6 feet) to mountainous regions in the interior. Taipei 101, the second tallest building in the world with more than 100 stories, reportedly swayed some 15 cm in Fanapi's winds.
Georgette soaks Baja
Tropical Storm Georgette has formed in the Eastern Pacific, just off the coast of Baja California. Georgette is just the seventh named storm of a near-record quiet season, and the first storm in the Eastern Pacific since Hurricane Frank died on August 28. Georgette's main threat is heavy rain, as the storm is expected to make landfall over Baja California later today and rapidly weaken into a tropical depression by Wednesday.
Elsewhere in the tropics
The GFS model predicts a series of three tropical distubances will develop in the Caribbean over the next 1 - 2 weeks. The NOGAPS model predicts a new tropical depression will form off the coast of Africa about seven days from now.
Third warmest August on record for the globe, and 2nd warmest summer, says NOAA
August 2010 was the globe's third warmest August on record, behind 1998 and 2009, according to the National Oceanic and Atmospheric Administration (NOAA) National Climatic Data Center (NCDC). NASA's Goddard Institute for Space Studies rated August 2010 the seventh warmest August on record. Both NOAA and NASA rated the year-to-date period, January - August, as the warmest such period on record. August 2010 global ocean temperatures were the sixth warmest on record, land temperatures were the second warmest on record, Northern Hemisphere temperatures the warmest on record, and global satellite-measured temperatures for the lowest 8 km of the atmosphere the warmest on record (Remote Sensing Systems data) or 2nd warmest on record (University of Alabama Huntsville data.)
The summer of 2010 was the second warmest summer on record, behind 1998, according to the National Climatic Data Center (NCDC), and the 4th warmest summer on record according to NASA's Goddard Institute for Space Studies. It was the warmest summer on record over land areas, and fifth warmest for ocean areas, according to NOAA.
For those interested, NCDC has a page of notable weather highlights from August 2010.
Figure 3. Departure of surface temperature from average for August, 2010. Image credit: National Climatic Data Center (NCDC).
La Niña intensifies and approaches the "strong" category
The equatorial Eastern Pacific Ocean is nearing strong La Niña conditions. Sea surface temperatures (SSTs) over the tropical Eastern Pacific in the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region", dropped to 1.5 - 1.6°C below average during the first two weeks of September, according to NOAA. The Australian Bureau of Meteorology put this number at 1.3°C below average (as of September 19.) Moderate La Niña conditions are defined as occurring when this number is 1.0°C - 1.5°C below average. Temperatures colder than 1.5°C below average would qualify as strong La Niña conditions. NOAA is maintaining its La Niña advisory, and expects La Niña conditions to last through the coming spring.
Both El Niño and La Niña events have major impacts on regional and global weather patterns. For the next month, we can expect La Niña to bring cloudier and wetter than average conditions to the Caribbean, but weather patterns over North America should not see much impact. Globally, La Niña conditions tend to cause a net cooling of surface temperatures. Thus, while the past twelve month period has been the warmest globally since record keeping began in 1880, the calendar year of 2010 may end up just shy of being classified as the warmest year ever.
August 2010 Arctic sea ice extent 2nd lowest on record
Northern Hemisphere sea ice extent in August 2010 was the second lowest in the 31-year satellite record behind 2007, according to the National Snow and Ice Data Center. Strong high pressure centered north of Alaska, combined with low pressure over Siberia (the Arctic Dipole Anomaly), acted together to produce a strong flow of warm air into the Arctic, causing the near-record melting. Ice volume in August was the lowest on record for August, according to University of Washington Polar Ice Center. Arctic sea ice is currently near its annual minimum, and 2010 will end up having the second or third lowest extent on record, behind 2007 (and possibly 2008.) The fabled Northwest Passage through the normally ice-choked waters of Canada, as well as the Northeast Passage along the coast of northern Russia, remained open for ice-free navigation as of September 21, and have been ice-free for a month. This is the third consecutive year--and third time in recorded history--that both passages have melted open. Mariners have been attempting to sail these passages since 1497, and 2005 was the first year either of these passages reported ice-free conditions; 2008 was the first year both passages melted free.
"Hurricane Haven" airing this afternoon
Tune into another airing of my live Internet radio show, "Hurricane Haven", at 4pm EDT today. The call in number is 415-983-2634, or you can post a question to email@example.com. Be sure to include "Hurricane Haven question" in the subject line.
Today's show will be about 30 minutes, and you can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast.
My next post will be Wednesday morning.
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